house physician vs MD

house physician and MD both are nouns.

Word	Noun	Adjective	Verb	Adverb
house physician	Yes	No	No	No
MD	Yes	No	No	No

As nouns, MD is a hypernym of house physician; that is, MD is a word with a broader meaning than house physician:

house physician: a physician (especially an intern) who lives in a hospital and cares for hospitalized patients under the supervision of the medical staff of the hospital
MD: a licensed medical practitioner

Other hypernyms of house physician include doc, doctor, Dr., medico, physician.

house physician (noun)	MD (noun)
a physician (especially an intern) who lives in a hospital and cares for hospitalized patients under the supervision of the medical staff of the hospital	a doctor's degree in medicine
	a Mid-Atlantic state; one of the original 13 colonies, with capital Annapolis
	a licensed medical practitioner